The battery pack for an electric or electronic device that may be used outdoors is required to be protected from the elements, in particular moisture. JP 2001-135289A discloses such a waterproof structure.
The battery pack can be protected from moisture by receiving it in a waterproof enclosure, but it requires a large number of components and increases the size of the device in which the battery pack is incorporated, particularly when a reliable waterproofing is intended.
However, the battery pack consisting of rechargeable batteries such as lithium ion batteries is fully enclosed and highly water-tight by itself, and the parts thereof that require protection are limited to the electric connector thereof. Even when moisture finds its way into a receptacle for the battery pack, no problem arises as long as the electric connector or the contacts thereof are not exposed to the moisture.